This invention relates to the field of data display modules, and more particularly to detachable data display modules that find application in selective call personal paging receivers.
Selective call personal paging receivers ("pagers") can be categorized according to the method they use to convey the transmitted message to the user of the pager. "Tone only" pagers simply emit a short audible tone to alert the user that he or she has a message, but do not actually transmit the message to the user. After receiving a "tone only" page the user typically calls a prearranged telephone number to receive the actual message. "Tone and voice" pagers include the necessary audio circuits and a small speaker to permit the user to hear a verbal message following the alert tone. Another category of pagers is "display" pagers which include a small alphanumeric character display whereby a short message, such as a telephone number, may be displayed. One advantage to "display" pagers is that they convey the message silently, maintaining the user's message in confidence.
In paging systems, each individual pager has a unique address code, and a base station activates a particular pager by first transmitting its unique address code. In a "tone only" system, only the address code need be transmitted to the pager. Recently developed paging systems now transmit address codes and other information to the pager using a digital format. Given such a digital system, a "display" pager uses the same basic circuits as a "tone only" pager, but additionally includes a display, display decoder circuitry, and circuitry or software to decode the message which follows the address code. Accordingly, to produce a "display" pager it is advantageous for a manufacturer to make a display module that attaches to its more basic line of "tone only" pagers. Therefore, by adding a display module with display decoder circuitry, plus additional software or hardware to decode the message, the "tone only" pager is upgraded to a "display" pager. This approach saves both development and manufacturing costs and permits the manufacturer to introduce a "display" pager into its product line that is based on a proven product.